Comparator in PriorityQueue vs ArrayList

Asked Oct 14 '15 at 18:57

Active Oct 14 '15 at 19:02

Viewed 31 times

I have been trying to implement PriorityQueue.

Here is what I wanted, sort according to the length of the String.

static class abc implements Comparator<String>
{

    @Override
    public int compare(String a, String b) {
        return a.length() - b.length();
    }

}

And the main Function:

    List<String> q = new ArrayList<String>();
    q.add("1");
    q.add("0111");
    q.add("11");
    q.add("151");
    q.add("121");

    Collections.sort(q, new abc());

This gave the perfect result.

But, when I used PriorityQueue instead of ArrayList

PriorityQueue<String> q = new PriorityQueue<>(10, new abc());

I don't get the required result.

When I print PQ:

System.out.println(q.toString());

[1, 151, 11, 0111, 121]

Also, since I want my List to be sorted overtime when I add a string, I would prefer PQ over ArrayList.

Can someone show with some example how to achieve this?

Thank you:)

edited Oct 14 '15 at 19:02

asked Oct 14 '15 at 18:57

Jay Patel

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1

What result do you get via priorityQueue? – Natalia Oct 14 '15 at 18:59
3

`PriorityQueue` will let you _extract_ elements in sorted order with `poll()`, but iterating over it or calling `toString()` on it will not return your elements in sorted order. This is part of how a priority queue works. – Louis Wasserman Oct 14 '15 at 19:02
Ohh, I got it.. Thanks – Jay Patel Oct 14 '15 at 19:05
1

Have you considered a `TreeSet`, or can your collection contain duplicates? – Paul Boddington Oct 14 '15 at 19:05

Comparator in PriorityQueue vs ArrayList

0 Answers0